Self-penetrating drilling method and thrust-generating tool for implementing same

ABSTRACT

The invention concerns a self-penetrating drilling method and a thrust-generating tool: the tool ( 1 ) comprises N blades ( 2   a,    2   b,    2   c,    2   d ). Each blade comprised K drill bits ( 3   a,    3   b,    3   c,    3   d ). The shapes, positions and orientations of said drill bits are determined in the following manner: the k th  drill bit of the last blade drills, at the (q−1) th  of the tool rotational cycle, a cut in the rock downstream of the one produced by the (k+1) th  drill bit of the first blade at the q th  rotational cycle of the tool; the k th  drill bit of the nth blade drills, at the q? th    rotational cycle of the tool, a cut in the rock downstream of the one produced by the k th  drill bit of the (n+1) th  blade at the q th  rotational cycle of the tool; the normal to the leading edge of the drill bit has a component along the axis of rotation oriented towards upstream.

[0001] This invention concerns an auto-penetrating drilling method and a thrust generating tool that makes the application of the method possible.

[0002] Current directed drilling methods are based on drilling wells using a lateral offset method that is becoming increasingly more widespread. Because of friction against the packing at the bottom of the hole in slanted and horizontal areas, the offset is limited since it is not possible to transmit sufficient weight behind the tool.

[0003] A solid block drilling tool is composed of two main parts: an internal part called “tool nose” whose drill bits dig into the bottom of the drill hole, and an external part called “tool flank” whose drill bits mainly dig into the walls of the drill hole. In particular, this invention deals with the cutting method of the cutting sub-structure that constitutes the tool flank. This invention also concerns the cutting sub-structure that makes the method application possible.

[0004] Method

[0005] Using a drilling tool that rotates around an axis, the method described in this invention consists of the generating of a thrust parallel to the direction of the said axis and oriented in the heading direction of the said tool in the rock.

[0006] Therefore it is possible to reduce or eliminate(auto-penetration) the need for weight behind the tool, and thus, also to increase the horizontal drilling extension potential.

[0007] In one application, the method is such that the thrust on said drilling tool is the result of the reaction of the rock on the drilling tool during the mechanical cutting action of the rock by the drilling tool.

[0008] Preferably, the tool consists of N blades, numbered from 1 to N in the inverse direction to that of the rotation action. Each blade is arranged in a spiral around the tool axis, and is positioned on a slanted angle compared to the tool axis. The blade part closest to the tool nose is also the closest to the tool axis. Each blade is composed of K drill bits. The first drill bit is that closest to the tool axis and tool nose. Each drill bit is identified with two reference indexes:

[0009] the first index n, variant from 1 to N corresponds to the number of the blade on which the drill bit in question is mounted,

[0010] the second index k, variant from 1 to k, corresponds to the position of the drill bit in question on the blade, beginning from the first drill bit.

[0011] Therefore, the k-th drill bit of the n-th blade will be defined as drill bit T(n,k).

[0012] Each drill bit has a face, hereafter referred to as driving face that makes the contact with the rock.

[0013] Preferably in this invention, in order to generate a thrust in the tool heading direction, the geometries, positions, and orientations of all or part of said drill bits are calculated respecting the following rules:

[0014] the k-th drill bit of the last blade T(N,k) cuts a groove in the rock to the (q−1)th rotation R(q−1) of the tool downstream of the groove cut by the (k+1)th drill bit on the first blade, T(1,k+1) at the q-th rotation Rq of the tool.

[0015] The k-th drill bit of the n-th blade, T(n,k) cuts a groove into the rock to the q-th rotation Rq of the tool downstream of the groove cut by the k-th drill bit of the (n+1)th blade, T(n+1,k), at the q-th rotation Rq of the tool.

[0016] The normal, or perpendicular to the drill bit driving face has a component according to the rotation axis in the upstream direction.

[0017] Tool

[0018] The invention also consists of an auto-penetrating drilling tool designed for well drilling in rock. The drilling tool that functions in rotation around an axis, consists of a sub-structure that forms the flank of the tool and that generates a thrust parallel to the direction of said axis and oriented in the heading direction of said tool in the rock.

[0019] According to one application method, the drilling tool is such that this thrust on said drilling tool is the result of the reaction of the rock on the drilling tool during the mechanical cutting action of the rock by the tool.

[0020] Preferably, the tool is composed of N blades numbered from 1 to N in the inverse direction to that of the rotation action. Each blade is arranged in a spiral around the tool axis, and is positioned on a slanted angle compared to the tool axis. The blade part closest to the tool nose is also the closest to the tool axis. Each blade is composed of K drill bits. The first drill bit is the bit closest to the tool axis and tool nose. Each drill bit is identified with two reference indexes:

[0021] the first index n, variant from 1 to N corresponds to the number of the blade on which the drill bit in question is mounted,

[0022] the second index k, variant from 1 to k, corresponds to the position of the drill bit in question on the blade, beginning from the first drill bit.

[0023] In this manner, the k-th drill bit of the n-th blade will be defined as drill bit T(n,k).

[0024] Each drill bit has a face, hereafter referred to as driving face that makes the contact with the rock.

[0025] The geometries, positions, and orientations of all or part of said drill bits are such that:

[0026] the k-th drill bit of the last blade T(N,k) cuts a groove in the rock to the (q−1)th rotation R(q−1) of the tool downstream of the groove cut by the (k+1)th drill bit on the first blade, T(1,k+1) at the q-th rotation Rq of the tool.

[0027] The k-th drill bit of the n-th blade, T(n,k) cuts a groove into the rock to the q-th rotation Rq of the tool downstream of the groove cut by the k-th drill bit of the (n+1)th blade, T(n+1,k), at the q-th rotation Rq of the tool.

[0028] The normal, or perpendicular to the drill bit driving face has a component according to the rotation axis in the upstream direction.

[0029] Other characteristics and advantages of this invention will be explained during the description of the variants of the invention application, given here as an example that is indicative but not limitative, and with the:

[0030]FIG. 1 that represents a view in perspective of a drilling tool as described in this invention, consisting of four blades and four drill bits per blade. This diagram also shows the local reference marks (Xi, Yi, Zi) and the total reference marks (Xo, Yo, Zo) that are used to define the position of the drill bits,

[0031]FIG. 2 that shows a view of a drilling tool from below,

[0032]FIG. 3 that shows the geometry of a drill bit,

[0033]FIG. 4 that shows the position and the orientation of a drill bit according to a local reference point (Xi, Yi, Zi),

[0034]FIG. 5 that shows a view in perspective of the interactions between the drill bits and the rock,

[0035]FIG. 6 that shows, in the case of a tool composed of four blades and two drill bits, the position and the order of the passage of the drill bits on a fixed plane of space, passing through the rotation axis of the tool,

[0036]FIG. 7 that shows graphically, in the case of a tool composed of four blades and two drill bits, the evolute of the cut structure according to the penetration axis and the order of the drill bit passage, and

[0037]FIG. 8 that shows a schematic view in perspective of the elementary interaction between a drill bit and the rock.

[0038] Below is a description of the variants of the implementation of the drilling tool according to this invention and shown in the diagrams.

[0039]FIG. 1 shows a view in perspective of a drilling tool 1 as described in this invention, composed of four blades 2 a, 2 b, 2 c, 2 d and four drill bits 3 a, 3 b, 3 c, 3 d per blade. This figure also shows a local reference mark (Xi, Yi, Zi) and the total reference mark (Xo, Yo, Zo) used to define the position (ri, zi, θi) of the drill bits. The tool functions in rotation around an axis 4 (axis Zo). The four blades (2 a, 2 b, 2 c, 2 d) are numbered 1 to 4 in the inverse direction 5 of the rotation. Conventionally, the first blade is that which is mounted with the drill bit closest to the tool axis; it is numbered (1) and corresponds to blade 2 a in FIG. 1. Blades 2 b, 2 c, 2 d are numbered respectively 2, 3, 4. Each blade 2 a, 2 b, 2 c, 2 d is arranged in a spiral rising around axis 4 of tool 1, and is positioned on a slant compared to the axis. The part, 2 a 1 of blade 2 a closest to the tool nose 1 is also closest to axis 4 of the tool.

[0040] Each blade is mounted with four drill bits. In this manner blade 2 a is mounted with drill bits 3 a, 3 b, 3 c, 3 d. Conventionally, the first drill bit of each blade is the closest to axis 4 and the tool nose 1. Therefore the first drill bit on blade 2 a is drill bit 3 a. Respectively, drill bits 3 b, 3 c, 3 d are the second, third and fourth drill bits mounted on blade 2 a. Each drill bit is identified by two reference indexes:

[0041] the first index n, variant from 1 to 4 corresponds to the number of the blade mounted with the drill bit in question,

[0042] the second index k, variant from 1 to 4, corresponds to the position of the drill bit in question on the blade, beginning from the first bit,

[0043] This way the k-th drill bit of the n-th blade will be defined as T(n,k). For example, the second drill bit 3 b on the first blade 2 a is defined as drill bit T (1,2).

[0044] Each drill bit has:

[0045] one face, hereafter referred to as driving face, that is in contact with the rock,

[0046] a cutting edge

[0047] a point of contact.

[0048] In the case of drill bit 3 b, T(1,2), the driving face bears the reference 3 b 1, the cutting edge bears the reference 3 b 2, and the point of contact bears reference 3 b 3. Using drill bit 3 b T(1,2) as a reference example, below is the explanation on how the local reference mark (Xi, Yi, Zi) is constructed, in order to define the position of drill bit 3 b T(1,2). Axis Zi is situated in the meridian plane passing through axis 4 and the point of contact 3 b 3. Axis Zi is on an angle βi compared to axis 4. Axis Xi is brought by the perpendicular to axis Zi situated in the meridian plane, passing through the point of contact 3 b 3. Axis Yi, perpendicular to axis Zi and axis Xi at point of contact 3 b 3, completes the ortho-normal reference point, since its origin is the point of contact 3 b 3. The co-ordinates of the origin of the ortho-normal reference points Xi, Yi, Zi, in the references XO, Yo, Zo, are Zi, ri, θi.

[0049]FIG. 2 shows the view of the drilling tool 1 from below and most of the elements that have been described can be recognised by referring to FIG. 1. Both figures show the same reference marking.

[0050] Using FIG. 3 as reference, below is the description of the structure and the geometry of an elementary drill bit (for example, drill bit 3 b). The bort 30, is presented in the form of a small plate in the shape of a quarter circle.

[0051] The quarter circle shape is not visible in FIGS. 1, 2, and 5, because part of the drill bit is set inside the blade for fixation. The hidden part of drill bit 3 c is shown with dotted lines in FIGS. 1, 2, and 5.

[0052] The bort 30, is incorporated into a structure 31, made of tungsten carbide, using a familiar method (soldering). FIG. 4 shows the driving face π1, reference 3 b 1, the cutting edge, reference 3 b 2, the point of contact with the rock, reference 3 b 3. FIG. 4 also shows the position relative to the tool flank π2, reference 32, and the lateral backing π3, compared to the driving face 3 b 1. The tool flank π2, 32, is visibly perpendicular to the driving face 3 b 1 as visibly parallel to plane (Xi, Yi). The lateral tool flank π3,33, is visibly perpendicular to the driving face 3 b 1 as well as plane (Xi, Yi). The notations α13, α12, α23, describe the dihedral angles respectively (π1,π3), (π1,π2), and π2,π3). Further on it will be shown how these angles preferably have particular values between 80° and 120°.

[0053] Below is a description of FIG. 4 that shows the position and the orientation of a drill bit in a local reference (Xi, Yi, Zi).

[0054] From hereon in the description, the following will be called:

[0055] cutting edge ωc, the slanting angle of the normal perpendicular Ni to the driving face 3 b 1 compared to plane Xi, Yi,

[0056] lateral angle ωs, the angle of axis Yi with the projection of the normal perpendicular Ni to the driving face 3 b 1 on plane Xi, Yi.

[0057] exit angle ωd, the angle of inclination of the cutting edge 3 b 2 compared to plane Xi, Yi.

[0058] It will be demonstrated further on that these angles preferably have special values as follows: the cutting angle ωc ranges between 0° and 40°, the lateral angle ωs ranges between 30° and 80°, and the exit angle ωd, ranges between 0° and 10°.

[0059] In order to generate thrust in the driving direction of the tool, the geometries, positions and orientations of all or part of said drill bits are calculated respecting the following rules:

[0060] the k-th drill bit of the last blade T(N,k) cuts a groove in the rock to the (q−1)th rotation R(q−1) of the tool downstream of the groove cut by the (k+1)th drill bit on the first blade, T(1,k+1) at the q-th rotation Rq of the tool.

[0061] the k-th drill bit of the n-th blade, T(n,k) cuts a groove into the rock to the q-th rotation Rq of the tool downstream of the groove cut by the k-th drill bit of the (n+1)th blade, T(n+1,k), at the q-th rotation Rq of the tool.

[0062] the normal, or perpendicular to the drill bit driving face has a component according. to the rotation axis in the upstream direction.

[0063] Below is the explanation of the rules with reference to FIGS. 5, 6, 7, and 8. FIG. 5 shows the view in perspective, of the interactions between the drill bits and the rock 51, the elements described with reference to FIG. 1. They have the same numerical reference marks. From hereon in the description PC (n, k) will define the point of contact of the drill bit (T(n, k). The oriented trajectories of certain points of contact have been marked using dotted lines with arrows (50).

[0064] It can be seen that the point of contact PC (4,4) of the drill bit (T (4,4) cuts a groove 51 a into the rock 51 upstream of the groove 51 b previously cut by another drill bit.

[0065] In the same way, it can be seen that the point of contact PC (1,4) of the drill bit T (1,4) cuts a groove 51 c into the rock 51 upstream of the groove 51 d previously cut by another drill bit.

[0066] In the same way, it can be seen that the point of contact PC (2,3) of the drill bit T (2,3) cuts a groove 51 e into the rock 51 upstream of the groove 51 f that will be previously cut by the point of contact PC(1,3) of drill bit T(1,3).

[0067] In the same way, it can be seen that the point of contact PC (2,1) of the drill bit T (2,1) cuts a groove 51 i upstream of the groove 51 j that will be previously cut by the point of contact PC(1,1) of drill bit T(1,1).

[0068] In the same way, it can be seen that the point of contact PC (2,2) of the drill bit T (2,2) cuts a groove 51 g upstream of the groove 51 h that will be previously cut by the point of contact PC(1,2) of drill bit T(1,2).

[0069] The diagram in FIG. 6 shows, in the case of a tool with four blades mounted with two drill bits, the position and the passage order 61 of the drill bits in a fixed plane that pass through the tool axis. It can be seen that as the tool rotates, the grooves 61 i are cut into the rock 60 by the drill bits, upstream of a groove 60 j, previously cut by another drill bit.

[0070]FIG. 7 shows graphically, in the case of a tool with four blades mounted with two drill bits, the evolute of the cutting structure according to the penetration axis (axis 2) and the passage order 61 of the drill bits.

[0071]FIG. 8 shows a schematic view in perspective of the elementary interaction between a drill bit T(n,k) and the rock 70. The driving face 71, is in contact with the rock in the clearance direction 72 of the drill bit, and cuts a groove 73. The drilling tool moves from upstream towards downstream in the direction shown by the arrow 74. The reaction force of the rock on the drill bit exercise the thrust directed in the direction of the arrow 74.

[0072] Below is a description of the main calculation stages used to determine the geometries, positions, and orientations of said drill bits aimed at obtaining the cutting methods that have been described immediately above, and the generation of the thrust oriented in the driving direction of the drilling tool in the rock;

[0073] first, the drive step is chosen according to tool revolution δcin.

[0074] then the lateral inclination slant βcin is chosen for the cutting plane according to drive step δcin. It must be noted that when the tool drills following its axis according to the drive step per revolution δcin, the grooves cut by the k-th drill bits of each blade during the same revolution are aligned according to a straight line slanted at an angle of δcin compared to the horizontal plane, as shown in FIG. 6.

[0075] the height h, and the width d, of the rectangular section of the elementary groove made by the drill bits are then chosen.

[0076] following this, the cut angle ωc, the lateral angle ωs, and the exit angle ωd, are chosen.

[0077] Now the lateral inclination slant βi of the drill bits are chosen in order to ensure that the tool flank π2 is not too close behind. The lateral inclination slant βi is the inclination of axis Zi of the i-th drill bit reference mark compared to the Zo axis as shown on FIG. 1.

[0078] The driving step δhel is chosen following Zo of the tool blades. The total of the drill bit points of contact of the same blade compose a helix wound around the axis z in the inverse direction to the rotation direction, whose step, marked as δhel, and constant for all blades, corresponds to the blade driving step. This driving step 75 is illustrated in FIG. 7.

[0079] Now the position (r11, z11, θ11) of the first drill bit on the first blade, is chosen.

[0080] At this point the position relative to the k-th drill bits on two consecutive blades is calculated.

[0081] Then a calculation is made of the position relative to the two consecutive drill bits on a same blade.

[0082] Preferably, the limits are fixed according to the following parameters:

[0083] the cutting angle ωc is lower than or equal to 30°.

[0084] the lateral angle ωs is higher than or equal to 60°.

[0085] the lateral inclination slant βcin of the cutting plane is higher than or equal to 50 °.

[0086] the lateral inclination slant of the drill bits βi is higher than or equal to the lateral inclination slant βcin of the cutting plane.

[0087] the height h, of the rectangular section of the groove is lower than or equal to 1 mm.

[0088] the width d, of the rectangular section of the groove is lower than or equal to twice the height h of the rectangular section of the groove.

[0089] With these explanations in hand, those skilled in the art are capable of determining the geometries, positions and orientations of said drill bits by consecutive iterations, in order to generate the thrust oriented in the driving direction of the drilling tool in the rock. 

1. Auto-penetrating drilling method for well drilling in rock (51); using a drilling tool (1) rotating around an axis (4), said method comprises the generation of a thrust parallel to the direction of said axis and oriented in the heading direction of the tool in the rock.
 2. Method according to claim 1; Blades Said tool is composed of N blades (2 a, 2 b, 2 c, 2 d) numbered from 1 to N in the opposite direction to the rotation direction (5); each blade being arranged in a spiral around the axis of the tool and on a slant with the tool axis; the part of the blade closest to the tool nose (1 a) is also the closest to the tool nose axis. Drill bits Each blade is mounted with k drill bits (3 a, 3 b, 3 c, 3 d); the first drill bit is the bit closest to the axis and the tool nose; each drill bit is i9dentified with two index references: the first index reference n, variant between 1 and N, corresponds to the number of the blade on which the drill bit in question is mounted, the second index reference k, variant between 1 and K, corresponds to the position of the drill bit in question on the blade starting from the first drill bit, In this way the k-th drill bit of the n-th blade will be identified as drill bit T(n,k); Each drill bit has a face, hereafter referred to as driving face (3 b 1) that makes contact with the rock (51); This method is such that, to generate a thrust in the heading direction of the tool, the geometries, positions, and orientations of all or part of the said drill bits are calculated respecting the following rules: the k-th drill bit of the last blade T(N,k) cuts a groove in the rock to the (q−1)th rotation R(q−1) of the tool downstream of the groove cut by the (k+1)th drill bit on the first blade, T(1,k+1) at the q-th rotation Rq of the tool. The k-th drill bit of the n-th blade, T(n,k) cuts a groove into the rock to the q-th rotation Rq of the tool downstream of the groove cut by the k-th drill bit of the (n+1)th blade, T(n+1,k), at the q-th rotation Rq of the tool. The normal, or perpendicular to the drill bit(3 b 1) driving face has a component according to the rotation axis (4) in the upstream direction. Tool
 3. An auto-penetrating drilling tool for well drilling in rock; said drilling tool (1) rotates around an axis (4) generating a thrust parallel to the direction of said axis, and oriented in the heading direction of said tool in the rock.
 4. Drilling tool as described in claim 3; blades Said tool is composed of N blades (2 a, 2 b, 2 c, 2 d) numbered from 1 to N in the opposite direction to the rotation direction; each blade is arranged in a spiral around the tool axis (4) and set on a slant compared to the axis; the part of the blade closest to the tool nose (1 a) is also the closest to the tool axis; drill bits Each blade is mounted with k drill bits (3 a, 3 b, 3 c, 3 d); the first drill bit is the bit closest to the axis and the tool nose; each drill bit is identified with two index references: the first index reference n, variant between 1 and N, corresponds to the number of the blade on which the drill bit in question is mounted, the second index reference k, variant between 1 and K, corresponds to the position of the drill bit in question on the blade starting from the first drill bit, In this way the k-th drill bit of the n-th blade will be identified as drill bit T(n,k); Each drill bit has a face, hereafter referred to as driving face (3 b 1) that makes contact with the rock (51); The geometries, positions and orientations of all or part of the said drill bits are determined by respecting the following rules: The k-th drill bit of the last blade, T(N,k) cuts a groove into the rock to the (q−1)th rotation R(q−1) of the tool downstream of the groove cut by the (k+1)th drill bit of the first blade, T(1,k+1), at the q-th rotation Rq of the tool. The k-th drill bit of the n-th blade, T(n,k) cuts a groove into the rock to the q-th rotation Rq of the tool downstream of the groove cut by the k-th drill bit of the (n+1)th blade, T(n+1, k), at the q-th rotation Rq of the tool. The normal, or perpendicular to the drill bit (3 b 1) driving face has a component according to the rotation axis (4) in the upstream direction. 